1. Field of the Invention
The present invention relates to hexagonal ferrite magnetic powder and to a method of manufacturing the same. More particularly, the present invention relates to hexagonal ferrite magnetic powder that is suitable for use as the ferromagnetic powder of a magnetic recording medium for high-density recording, and to a method of manufacturing the same.
The present invention further relates to a magnetic recording medium comprising the above hexagonal ferrite magnetic powder.
2. Discussion of the Background
Conventionally, ferromagnetic metal magnetic powder has primarily been employed in the magnetic layers of magnetic recording media for high-density recording. Ferromagnetic metal magnetic powder is comprised primarily of acicular particles consisting mainly of iron. To achieve high-density recording, efforts have been made to reduce the size of the particles and increase their coercive force. They have been employed in magnetic recording media used in various applications.
With the increase in the amount of information being recorded, ever higher density recording has been demanded of magnetic recording media. However, in achieving even higher density recording, limits to the improvement of ferromagnetic metal magnetic powder have begun to appear. By contrast, magnetic recording media with magnetic layers in which hexagonal ferrite magnetic powder is employed have better high-density characteristics in their vertical components. Accordingly, hexagonal ferrite magnetic powder is ferromagnetic material that is suited to achieving even higher densities. Thus, in recent years, various investigation has been conducted into magnetic recording media employing hexagonal ferrite magnetic powder (for example, see Japanese Unexamined Patent Publication (KOKAI) No. 2011-178654; Japanese Unexamined Patent Publication (KOKAI) No. 2012-142529 or English language family member US2012/177951A1; Japanese Unexamined Patent Publication (KOKAI) No. 2012-204726 or English language family member US2012/251844A1; Japanese Unexamined Patent Publication (KOKAI) No. 2006-120823; Japanese Patent No. 4675581; and Japanese Unexamined Patent Publication (KOKAI) No. 2010-239067, which are expressly incorporated herein by reference in their entirety).